This invention relates to horizontal metal extrusion presses and more particularly to a composite ram cylinder therefor to eliminate eccentric displacement of the cylinder sleeve with respect to the cylinder head.
Metal extrusion presses are preferably arranged horizontally in order that the removal of the extruded sections, which are frequently highly susceptible to bending, can be kept simple. The press force of single-cylinder presses is limited by what is possible in manufacturing, in particular casting, during the production of the press cylinders. Only a few foundries are capable of producing castings of unusual size, and the costs of production increase disproportionately to the risk of defective castings and the steps for preventing them. In addition, the service life of large cylinders is not always satisfactory as a result of differing expansion and stressing of the cylinder wall and the cylinder end or head, with tension peaks occurring in the transition region. In order to avoid these drawbacks, it is known to make cylinders in two parts and to construct them from a sleeve and a head. Such a construction is known for example from German Patent DE-B-1 231 559 or U.S. Pat. No. 2,075,968. The cylinder head of such a press forms a plug provided with a seal with respect to the sleeve and with a flange. A horizontal metal extrusion press is known from German Patent DE-B-1 627 837, which discloses ram cylinders in two parts, in which the cylinder head and the cylinder sleeve are clamped axially together by screw bolts. This clamping cannot prevent the cylinder sleeve from being displaced under its inherent weight eccentrically with respect to the cylinder head and hence with respect to the press axis during the expansion of the cylinder sleeve under the operating pressure and the thereby resulting play of the cylinder sleeve with respect to the plug of the cylinder head or end, which is not acceptable for the wear of the components of the extrusion press or for the extrusion pressing procedure and renders the pressing of hollow sections of precise size impossible.
To exceed the press force which can be attained in a one-piece cylinder, horizontal metal extrusion presses are therefore in general built as multiple-cylinder presses, at the cost of greater structural outlay and higher costs.
On the basis of the state of the art according to German Patent 1 627 837, the object of the invention is to permit the use of a composite cylinder in a horizontal metal extrusion press in such a way as to eliminate eccentric displacement of the cylinder sleeve with respect to the cylinder head.